A maniac doused a city bus driver and several passengers with what is believed to be pepper spray in Harlem today, in the latest of a string of seemingly unprovoked attacks on MTA employees, police said.

The female driver and three passengers were so sickened by the 1:30 p.m. attack at 125th Street and Lexington Avenue that they had to be treated at a hospital, cops said.

Police say a Hispanic man in his 30s walking outside the bus approached the vehicle as it was stopped on 125th Street, then sprayed the driver through an open window, apparently at random.

Lisa Tucker, 47, of Harlem, was in a nearby furniture store when the brazen attack occurred, and called 911 as stunned passengers fled the bus in agony. Passengers told her the man knocked on the driver’s-side window and sprayed the driver when she opened it — and then just strolled off.

“A big guy was outside screaming, ‘My eyes! My eyes are killing me!’,” Tucker said. “(The attacker) hit three or four people at the same time … and the people said he just walked away. Like normal.”

The driver and six passengers in all were sickened, but three passengers were treated on scene and refused a trip to the hospital. The driver and three other passengers were taken to Mount Sinai Hospital for skin and eye irritation and difficulty breathing.

Today’s pepper-spray attack comes on the heels of several assaults on city bus drivers, including a terrifying syringe stabbing in Brooklyn on Sept. 24.

In that case, driver Markanthony Salandy was stabbed from behind by a deranged passenger who had snuck on board without paying.

The alleged stabber, Shelwyn Patt, 53, is charged with attempted murder and assault. He is free on $7,500 bail, but is barred from riding any city buses,

Salandy, the driver stuck with the syringe, fears the needle contained HIV — but he won’t find out whether he’s been infected for about six months.

Metropolitan Transportation Authority spokesman Charles Seaton said the MTA is installing more shields and security cameras to protect drivers, and will launch a program encouraging witnesses to assaults to come forward.

“We certainly consider an attack on any of our employees as an attack on all of us,” Seaton said. “Bus operators, these are people out there serving New Yorkers every day.”